THEMIS Takes Deimos’ Temperature

Can you feel the heat? NASA’s Mars Odyssey can see it! This is an image of Mars’ smaller moon Deimos, captured with Odyssey’s THEMIS (Thermal Emission Imaging System) instrument on Feb. 15, 2018. Part of the 7-mile-wide Moon was in shadow, but the sunlit surface area reached temperatures up to 200 K (that’s still pretty cold for us, though… –100ºF / -73ºC!)

This was the first observation of Deimos by Mars Odyssey; the spacecraft first imaged Mars’ other moon, Phobos, on September 29, 2017. Researchers have been using THEMIS to examine Mars since early 2002, but the maneuver turning the orbiter around to point the camera at Phobos was developed only recently. (Source: NASA)

Mars isn’t a planet well-known for its natural satellites but it actually does have two small moons. The larger, Phobos, is an irregularly-shaped, heavily grooved and cratered world only about 17 miles (27 km) across at its widest. But Phobos has an even smaller companion: Deimos, which at 7.5 miles across is less than half Phobos’ size.

Deimos is much further away from Mars than Phobos too. With a mean distance of 13,268 miles (21,353 km) from the surface of Mars it’s over 2 1/2 times farther away. Little Deimos travels quickly though—it only takes it bout 30 hours to complete one orbit.

Deimos imaged by HiRISE aboard MRO (NASA/JPL-Caltech/ASU)

Mars Odyssey launched on April 7, 2001 and arrived at Mars on Oct. 24, 2001. The Thermal Emission Imaging System (THEMIS) is a special camera on the Mars Odyssey spacecraft developed and run by Arizona State University. Its main tasks are mapping rock mineralogies and detecting heat, which yields information on the physical and thermal properties of the Martian surface. (Via ASU)